The present invention is directed to a power transistor for the microwave range.
Power transistors are usually designed as structures with several strip-shaped emitter supply lines ("Multi-Emitter Finger-Structures") (see e.g. G. W. Wang et al: "Design Optimization of Microwave Power Heterojunction Bipolar Transistor Cells," 1989 IEEE MTT-S Digest, 1061-1064 and A. P. Long et al: "2.5 W, C-volume, GaAs/AlGaAs Heterojunction Bipolar Power Transistor," Electr. Lett. 25, 979-981 (1989)), both incorporated herein. In the heterobipolar transistor, the observed thermal resistance leads to increased operating temperatures in comparison to MESFET power transistors. This significantly limits the CW power output. The high breakthrough voltages at the heterobipolar transistor and the possibility to handle currents of high intensity can therefore not be optimally used. Desirable are power transistors which can be operated up to frequencies in the microwave range (10 to 100 GHz) with high outputs (e.g. 5 W at 30 GHz).